Variation of clinical outcomes used in glaucoma randomised controlled trials: a systematic review

In randomised clinical trials (RCTs) the selection of appropriate outcomes is crucial to the assessment of whether one intervention is better than another. The purpose of this review is to identify different clinical outcomes reported in glaucoma trials.

We conducted a systematic review of glaucoma RCTs. A sample or selection of glaucoma trials were included bounded by a time frame (between 2006 and March 2012). Only studies in English language were considered. All clinical measured and reported outcomes were included. The possible variations of clinical outcomes were defined prior to data analysis. Information on reported clinical outcomes was tabulated and analysed using descriptive statistics. Other data recorded included type of intervention and glaucoma, duration of the study, defined primary outcomes, and outcomes used for sample size calculation, if nominated.

The search strategy identified 4323 potentially relevant abstracts. There were 315 publications retrieved, of which 233 RCTs were included. A total of 967 clinical measures were reported. There were large variations in the definitions used to describe different outcomes and their measures. Intraocular pressure was the most commonly reported outcome (used in 201 RCTs, 86%) with a total of 422 measures (44%). Safety outcomes were commonly reported in 145 RCTs (62%) whereas visual field outcomes were used in 38 RCTs (16%).

There is a large variation in the reporting of clinical outcomes in glaucoma RCTs. This lack of standardisation may impair the ability to evaluate the evidence of glaucoma interventions.